Field of the Invention
The present invention relates to a method for measuring an axial force of a bolt; and, more particularly, the present invention relates to a method configured for measuring an axial force of a bolt using vibration characteristics occurring when fastening a joint using a fastener.
Description of Related Art
In various industrial fields, including machinery, plant, and power plant turbines, a stable fastening force of bolts has been required as advanced machinery and structures become larger.
Furthermore, an internal combustion engine is one of the more critical component that outputs kinetic energy in a vehicle, and is therefore necessary to manage a fastening force of the engine in the production of the engine.
Although poor fastening of the engine has various causes, the poor fastening is representatively accompanied with vibration and noise when the engine is driven. In the related art, a skilled worker drives a completed engine and detects vibration or noise occurring in the driven engine by feel or ear to detect the poor fastening of the engine. However, the present method has a limit in estimating the fastening force of a fastener and thus the poor assembly of the engine.
A method of measuring a fastening force (axial force) of a bolt using ultrasonic waves is used as an alternative to the method using such a human detection. The method of measuring a fastening force (axial force) of a bolt using ultrasonic waves is a method of measuring a change (deformation) in length of the bolt by its axial force using a time-of-flight of an ultrasonic wave to determine an axial force from elastic properties of a material.
The method of measuring an axial force of a bolt using ultrasonic waves is advantageous in that the method can standardize axial force measurement, compared to a mechanical method in which measurement taking is inconvenience, costly, and time consuming.
However, the method of measuring an axial force of a bolt using ultrasonic waves is disadvantageous in that, since the head or end portion of the bolt has a non-planar surface, echo signals are erroneous or the length of the bolt should be accurately measured before the bolt is fastened. Hence, the provided method is not properly utilized in the field.
Accordingly, there exists a demand for a method of measuring an axial force of a bolt, which is configured for increasing utilization in the actual field and of increasing accuracy/precision of the axial force measurement.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.